And while they wish it would have happened any other way, the family's shared oligodendroglioma diagnosis has made them closer.

"That's been the silver lining in this mess of a situation," Zach says.

His dad, Brock, agrees.

"We're connected at a level that most people don't know exists," he says. "The love that we feel and express as a family is just different because of that."

Spencer's oligodendroglioma diagnosisThe family's oligodendroglioma journey started in August 2008. That's when Spencer suffered his first seizure, and it wasn't long before he endured another and another. Spencer was 16, traveling with his soccer team and preparing for a doubleheader. The first focal seizure occurred in his right arm during the first game, then a second seizure during the second game. A few months later, he suffered a third.

His family knew they had to get to the bottom of this. They met with multiple doctors over the next few months.

After an MRI, doctors told Spencer they needed to perform surgery right away. He was diagnosed with oligodendroglioma, a type of brain tumor that is more common in adults ages 40 to 50 and is commonly referred to as oligo.

Spencer deferred college for a year to focus on his health. In April 2010, he had another focal seizure, letting him know that the tumor was still active, and started a year-long round of chemotherapy. Zach's oligodendroglioma diagnosisA few months later, the Greenes took a family vacation to Mexico. Not long after they arrived, Zach, then 21, suffered a grand mal seizure.

The Greenes cut their trip short and returned to their home in California to take Zach to the doctor.

A few weeks later, Zach underwent brain surgery to remove the tumor. Just like his younger brother, Zach had oligodendroglioma.

Coming to MD Anderson for oligodendroglioma treatment Spencer underwent chemotherapy in two, year-long cycles between 2010 and 2012, while Zach underwent quarterly MRIs to monitor if the oligodendroglioma was coming back. In fall 2013, both boys learned they'd need surgery again. And, post-surgery they found out that their oligodendroglioma had progressed to a grade 3, which typically requires radiation treatment.

But to Brock, traditional radiation treatment was not a good option for them. He began researching and found MD Anderson's proton therapy program.

In winter 2013, Spencer underwent two months of proton therapy and completed his treatment the last day of the year. Six months later, his older brother followed in his footsteps, coming to MD Anderson for two months of proton therapy treatment. He completed his treatment on June 30, 2014.

Both Spencer and Zach were struck by the kindness the staff showed.

"I felt like we were not only in great hands, but caring ones," Spencer says. "And for someone who is battling something like this, that holds a lot of weight."

Raising awareness of oligodendrogliomaThroughout their brain tumor journey, the Greenes were struck by how little research there is on brain tumors and found that there was almost none on oligo. They decided to take action, and started a nonprofit organization to raise awareness and money for oligodendroglioma research.

Seeing not one but both of his sons struck by brain tumors, Brock initially felt powerless. But funding research has helped the Greenes get back that power.

"And that," he says, "is a really good feeling."

Today, both brothers have returned to their everyday lives. Zach is working on a Ph.D. in astrophysics at Columbia University in New York, and Spencer is finishing up his bachelor's degree at Denison University in Ohio. But they still make time to organize fundraisers like walks and runs.

The financial and emotional support from friends and strangers alike has provided a big and ongoing morale boost.